On the Evolution of the Annual Cycle in the Tropical Pacific

Extraction of the accurate annual cycle in the tropical Pacific sea surface temperature field is addressed as a demonstration of the utility of a new technique called the cyclostationary empirical orthogonal function (CSEOF) analysis. The strength of the annual cycle has fluctuated roughly by 15% in the past 30 yr (1970–99), and this fluctuation includes swings every 4–6 yr. Accurate extraction of the detailed structure and temporal modulation of the annual cycle was owing to the application of CSEOF analysis, the concept of which has been introduced and compared to the conventional EOF analysis.